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.lunuarv 15, 2008 Pgge 30 <br />P'OS _ tan(uctual friction angle) (Eqn. 8) <br />tan(.triction ulwle crt , failure ) <br />4.4 Analysis Results <br />The results of the analysis are summarized in Table 5. 'T'he most relevant case for <br />recommending maximum spoil pile heights is Case #4c for the average bedding dip of 13° and <br />Case 45c for the steepest bedding of25°. Onl} results from these two cases are presented here. <br /> 'Table 5. Summary of Results for Cases Analyzed <br /> Slope Filllleight Spoil <br /> (11:x')/ above Q- Bedding Bedding Spoil Friction at <br /> Angle Floor at Tex Dip Friction Cohesion Lim of Equi Safety <br />Case (°) (ft) (°) (°) (f) (°) Factor <br />4a 1.3 ! 37.6 205 13 5 U 51 Unstable <br />4h 1.3 /37.6 137 13 5 0 46 Unstable <br />4c 1.3 ' .3 7.6 68 13 5 0 38 1.07 <br />5a 1.3 /37.6 50 25 15 0 55 Unstable <br />5b 1.3 /37.6 40 25 15 5 47 Unstable <br />5c 1.3/37.6 30 25 15 50 38 1.07 <br />'Depth from Ground to Q-I lour k 217 ft <br />Case 44c had a spoil slope face of 37.6° (1.311:1 V) and a spoil pile height of 68 a above <br />the toe. The groundwater table was assumed 1 11 above the weak Q-Floor nutdstone to represent <br />saturated mudstune but drained spoils. The initial spoil strength parameters were 0 = 55°. (' = 0, <br />7' 0. 'T'he initial peak bedding plane strength was assumed to be 0, = 15° for tile Q-Floor <br />mucWone. <br />The equilibrium state was computed assuming no groundwater elects: drained, <br />unsaturated conditions. 'The groundwater table was then introduced and the mass density below <br />the phreatic surface was adjusted to simulate saturated conditions and the model rerun to <br />equilibrium. 'The Q-Floor mudstune strength was then reduced to a residual strength condition <br />(0, = 5°) to represent long-term softening of the Q-Floor on the inclined bedding. 'T'he limit of <br />equilibrium state was reached when the spoil friction was reduced to 38°. <br />Contours of velocity, shown in Figure 18, illustrate the unstable area of the spoil pile. <br />The gray area has low velocities which are considered negligible. The model is not in an <br />equilibrium state and, thus, the slope is considered unstable tinder these conditions. 'The failure <br />mode is indicated by a circular slip mechanism in the spoil pile: not unstable slip along bedding. <br />The case with the next increment ofspoils added had higher velocities and also did not come to <br />an equilibrium condition at spoil friction above 40°. 'The safety factor for this case of 68 fl of <br />spoils is FOS = 1.07. <br />Agapito Associates, Inc.